Back rest or support for a chair, seat, or the like



Hume 9 A. H' GAB@ ill BCK REST OR SUPPVORT FOR A CHAIR, SEAT OR THE LIKE Filed Jan. 29, 1935 Patented June 9, 1936 UNITED STATES PATENT OFFICE BACK REST OR SUPPORT FOR A CHAIR, SEAT, OR THE LIKE pany Application January 29, 1935, Serial No. 3,921 In Great Britain February 7, 1934 1 Claim. Y (Cl. 155-157) The present invention has relation to a backrest or support for a chair, seat, or the like, more particularly the type of device wherein an upright arm supporting a backrest member is ad- 5 justably clamped toa tment at the rear of the seat, the present invention having for its object to provide a considerable range of adjustment of the backrest member vertically, forwardly, and rearwardly, also a speedy xing and secure maintenance of the said backrest member when adjustment has been determined.

According to the present invention a link pivoted to a fitment adjacent the rear of the seat is provided with duplex serrated clamp mechanism adapted for simultaneous control from a single hand screw member, one serrated clamp mechanism being adapted to secure the link or linkage in position of adjustment in relation to the seat tment and the other serrated clamp mechanism 20 being associated with the backrest supporting arm adapted tosecure same in any desired position of angular adjustment.

In order that this invention may be clearly understood and readily carried into practice, ref- 25 erence may be had to the appended explanatory sheet of drawings, upon which:-

Figure 1 illustrates in fragmentary plan view adjustable clamping mechanism for a chair backrest constructed according to the present in- 30 vention.

Figure 2 illustrates the mechanism in sectional elevation taken on the line 2-2 of Figure 1;

In a convenient embodiment of the present invention the seat frame of the chair is provided 35 with a rearward extension or part in the form of two plate-like projections a. Mounted upon these plate-like projections is a U-shaped strap a1 having a superimposed cross member m for supporting the seat n said strap a1 and projections 40 supporting a spindle b hereinafter referred to as the forward spindle. Pivotally mounted upon this spindle b are two links c and d, one of which (c) is a straight plate-like link and the other (d) provided with annularly serrated formations d1 45 d2 at its extremities. The free extremities of these links are coupled by a spindle e hereinafter referred to as the rearward spindle. A serrated boss f is mounted upon the forward spindle b and is secured against rotation by means of a 50 strap f1 attached to one of the plate-like projections a, the serrations upon this boss co-operating with those d1 upon the associate link d. Mounted upon the rearward spindle e" is a boss y having a serrated face adapted to co-operate with the serrated face d2 on the associated extremity of the serrated link d, this said boss having attached thereto a supporting arm h carrying a backrest at its upper part. A pressure plate 5 i is utilized for closing the serrated clamps, the said pressure plate at its one extremity i1 being apertured and mounted at one extremity ofthe forward spindle b against the transverse pin b1, and the other extremity i2 being apertured and 10 loosely engaged with a screwed extension e1 upon the rearward spindle e. A hand screw member j is mounted upon the spindle extremity e1, and the intermediate part i3 of the pressure plate is cranked inwardly as shown to co-operate with the central part of the link d. The respective serrated faces of the clamps g d2 d and f d1 d are normally urged apart by appropriately incorporated compression springs 7c Z mounted respectively upon the spindles e and h, and it will be appreciated that by seizing the backrest h with the hand and releasing the hand screw j on the rearward spindle, freedom is imparted to the linkage so that the back can be tilted at any desired angle, and further elevated or depressed by means of the linkage in the manner implied by dotted lines (Figure 2). When a desired adjustment has been obtained, a tightening of the hand screw 7 ensures by means of the pressure plate a closing of both clamps, a correct relative setting and xing of the links and backrest.

What I claim as my invention and desire to secure by Letters Patent is:

A backrest for a seat comprising in combination projections upon the rear of the seat frame, a spindle spanning said projections, two links pivoted to the spindle, a further spindle spanning said links at their free extremities, a backrest post pivotally mounted upon the further spindle between the outer extremities of the links, means comprising interengaging serrated faces interposed between the backrest post and one of the links, and further serrated faces interposed between a fixed member on one of said projections around the first-mentioned spindle and one of said links, a pressure plate pivoted to one of said spindles for movement radially and transversely thereof and engaged with the further spindle, and a hand screw member upon said Vfurther spindle and a projection upon said pressure plate contacting one of the links.

ARCHIBALD HORSFIELD GABB. 

